zstd: translate fseDecoder.buildDtable into asm #598
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WojciechMula
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I paused development but finally, get back to this translation. (Some tests still don't pass and for now, I can't figure out why.) |
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@WojciechMula Great to have you back! What is the failure? |
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@klauspost A funny thing - when reviewing diff on github minutes ago I immediately spotted a mistake. :) I put wrong condition in loop (JLE rather JL). |
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@WojciechMula Having some time away from code will often do that :) |
WojciechMula
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I have many years of experience, but this property of our brain still amazes me. :) |
| MOVWQZX(ptr, nextState) | ||
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| // symbolNext[symbol] = nextState + 1 | ||
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Hmm, maybe simple INCQ(ptr) won't be bad?
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Quick benchmarks showed more regressions, but maybe it's just noise.
zstd/_generate/gen_fse.go
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| // newState := (nextState << nBits) - tableSize | ||
| newState := GP64() |
zstd/_generate/gen_fse.go
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| SHLQ(reg.CL, newState) | ||
| SUBQ(b.tableSize, newState) | ||
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Remove, some remnants from debugging
Regression from #598 causing excessive heap allocations.
Regression from #598 causing excessive heap allocations.
In our tests,
buildDtabletakes 6-7% of the total time, so seems it's worth trying to make it a bit faster.Below are the results from a Skylake machine (my IceLake AWS instance is temporarily unavailable). No significantly faster, but overall a faster and just a few regressions.